Computer networks and systems are designed and operated very differently from one to another.
Computer networks are usually shared simply i.e. without any particular contract or offer of guarantee particularly in respect of performance. Computing or storage systems and more generally the so-called “open” systems remain private and physically isolated at least regarding their own function.
To date there is no possibility of guaranteeing a performance or power level which could then be offered to a user for the use of a set of resources, a network or open system, optionally combined, for example via a rental contract.
Basically, wide area networks chiefly use the transmission of data in the form of formatted packets delivered following the Internet Protocol. The service offered by this Internet Protocol is of “best effort” type. The Internet Protocol provides for best effort delivery having regard to communication resources, in particular links and gateways, and to available computing resources in the network.
Some applications of wide area networks require guaranteed data delivery times and/or delivery rates. For video or music broadcasting for example the data is transmitted in the form of a signal sampled at a fixed frequency, and this signal must be reconstructed and restored to the receiver at this same frequency. Although these applications are able to accommodate variations in delivery time and/or rate to a certain extent, they nevertheless require a limited delivery time (of the same order of magnitude as the sampling period of the emitted signal) and a minimum delivery time so that the receiver is able to benefit from the quality and fluidity of the data such as broadcast (emitted).
In such cases, “best effort” transmission is not truly satisfactory.
It is possible, in a wide area network, to construct what is called a virtual private network. In this case, part of the transmission capacity can be dedicated to the virtual private network. The capacity thus immobilised for the virtual private network is generally greater than its actual needs; the intrinsic capacities of the private network link, in particular its bandwidth, may exceed needs and/or there are periods of time during which this virtual private link is not used. As a result, the total transmission capacity of the wide area network, including its time dimension, is ill-used.
At the present time, there is generalised use of Internet type networks. It is therefore desirable to make provision so that all types of data are able to transit on such networks, whether data accommodating the “best effort” approach, or on the contrary data which requires performance guarantees with respect to transmission rate and/or delivery time. The issue at stake is what is sometimes referred to as “the Internet of the Future”.